A reamer, or endodontic reamer, is a surgical tool used for endodontic procedures, most often a root canal. A reamer is often used in conjunction with a file to clean out the inside of the root canal and prepare it for the root canal filling material. Root canal fillings can be done with amalgam, composite resin, nickel, or least often, zirconium dioxide. A reamer is designed to be able to thoroughly debride the interior of the root canal to the apical foramen so it can be disinfected prior to filling. A reamer is created by twisting a triangular or square shaft just enough to create cutting edges that are approximately parallel to its axis. The reamer is inserted into the root canal and rotated 1/4 or 1/2 turn, which scrapes the walls of the canal allowing it to be thoroughly debrided. The reamer must be loosely touching the interior walls of the canal.